Crown slitter



Nov. 6, 1934. J. s. HAGOBIAN CROWN SLITTER Filed Dec. 15

ATTORN EYS Patented Nov. 6, 1934;

UNITE j CROWN SLITTER 3 Claims.

, This invention relates to new and useful improvements in dental instruments, and has particular relation to crown slitters such as are used to slit dental crowns in order that the crowns, or the crowns and bridge work held by them, may be removed from the mouth of a patient.

An object of the invention is to provide a crown slitter which is so constructed that a dentist using the same can get to the back or distal portion of a crown to slit it, so that when the crown is replaced the soldered joint closing the slit is at the back of the tooth and will not be noticeable.

Another object is to provide a crown slitter having the characteristics stated and which is so constructed as'not to engage or injure the teeth or lips at one side or portion of the mouth while being used to slit a crown at the other side or in another portion of the mouth.

Other objects and advantages will become apparent from a consideration of the following detailed description taken in connection with the accompanying drawing wherein a satisfactory embodiment of the invention is shown. However,

it will be understood that the invention is not limited to the details disclosed, but includes all such variations and modifications as fall within the spirit of the'invention and the scope'of the appended claims.

In the drawing:

Fig. 1 is a top plan view illustrating a crown slitter constructed in accordance with the present invention;

Fig. 2 is a side elevational view thereof, the view being taken looking toward the lower side of Fig. 1;

Fig. 3 is a view taken substantially along the plane of the line 33 of Fig. 1;

Fig. 4 is a sectional view taken substantially along the line 4.-'-4 of Fig. 3;

Fig. 5 is a top plan View of the knife portion of the tool or instrument;

Fig. 6 is a view illustrating the instrument in use; I

Fig. '7 is a view somewhat similar to Fig. 6 but on a larger scale;

Fig. 8 is a View somewhat similar to Fig. 7 but showing the improved crownslitter in use in slitting a crown at the distal side thereof, or at the side thereof remote from the relatively heavy solder used to securea bridge to an abutment crown;

Fig. 9 is a view somewhat similar to Fig. 1 but showing the tool reversed in construction for operation in the portions of the mouth not taken care of by the construction of Fig. 1; and

Fig. 10 is a view somewhat similar to Fig. 2 of one end portion of the instrument but showing a modified pivotal connection.

The instrument as disclosed in Figs. 1 through 8 and 10 is made up for operation on the upper palatal left and lower lingual right of the teeth. In Fig. 9 the instrument is shown as made up for use on the upper palatal right and lower lingual left of the teeth. In either case the instrument is the same, it being merely necessary to reverse the bends of the parts as will later more fully appear.

Referring first particularly to Figs. 1 through 8, my improved crown slitter includes a pair of members 11 and 12 of which the member 11 toward one of its ends is shown as passing through the member 12 and is pivotally connected with it as by a rivet or the like 13. From this it will be seen that the pivot 13 divides the members 11 and 12 into handle portions 14 and 15 and jaw portions 16 and 17 respectively. At its forward end jaw portion 16 may be enlarged to provide a bearing portion 18 hollowed at its under side as shown at 18a and designed to, in the use of the tool, engage the occlusal surface of a crown as, for. example, the crown 19 shown in Fig. 7 or the crown 20 of Fig. 8. The forward end of jaw 17 is sharpened providing a knife 21. This knife is preferably curved transversely as shown in Fig. 5, although not necessarily so, and is designed to form a vertical slit in a crown when the improved instrument is in use.

In the use of the device the jaw 16 has its end 18 engaged against the occlusal surface of a crown and the knife 21 is engaged with the inner end or edge of the crown next to the gum. It will be noted that the end 18 of jaw 16 extends slightly beyond the knife 21. When the parts are arranged as stated, pressure may be exerted to force the handles in the direction of one another. The handle 15 does not move and as the handle 14 approaches the handle 15 the knife 21 slits or cuts thev crown lengthwise so that it maybe removed from a tooth or tooth root.

At 22 the members 11 and 12 are laterally offset in the same direction and in a direction longitudinally of the pivot 13. This offset or curve 22 is at the handle side of the pivot, and at the other side of said pivot the jaw portions 16 and 1'7 are curved or offset at 23, this last curve or offset being in the same general plane as the curve or ofiset 22 but in the opposite direction. At the outer end of the curve or offset 23 the jaws are again curved at 24. to have their free end portions extend in angular relationship to their body portions so that the bearing portion 18 of jaw 16 and the knife 21 of jaw 17 are laterally disposed relative to the portions of the jaws adjacent the pivot 13.

With this construction the dentist using the instrument may slit a crown in its rear or distal portion. This is as shown in Figs. 6 and 7, and in these figures it will be noted that the knife 21 is so located as to slit the crown 19 at its inner or disto-lingual portion. Therefore, if the crown is to be replaced in the mouth of the patient the solder closing the slit will be so located as not to be noticeable. It is the curves or oifsets 22 and 23 and the angular relationship of the free end portions of the jaws to the body portions thereof that enables the dentist to more easily reach the rear or distal portions of the crowns. Without these features of construction the crowns must be slit on their labial or buccal surfaces as the case may be when they are to be removed, and then when they are replaced the solder closing the slit is at the front of the crown and is very noticeable. This last is particularly true of the front teeth. With the present slitter crowns in the anterior portion of the mouth may also be slit on their lingual or palatal surfaces.

With the instrument of Figs. 1 through 8 the operator may easily reach the rear or distal portion at the upper palatal left and lower lingual right and with the instrument of Fig. 9 the operator may reach the rear or distal portion at the upper palatal right and the lower lingual left of the teeth. The instrument of Fig. 9 is made up as the instrument of the other figures but simply has its curves or offsets reversed. That is, the curves 25, 26 and 2'? of Fig. 9 correspond with the curves or offsets 22, 23 and 24 respectively of Fig. 2. Otherwise, the instruments are the same and bear the same reference characters. Fig. 8 illustrates the use of the improved crown slitter as used to slit the rear crown 20 of a bridgework 28 in the lower right jaw. In such figure it will be noted that the slitter is so constructed as to enable the dentist to slit the crown in its thin portion rearwardly of the heavy solder 29 securing or anchoring the bridge 28 to the abutment crown 20. The curve in the knife 21 as shown in Fig. 5 also facilitates reaching this location and permits cutting the crown with the knife edge at substantially right angles or normal to its surface as shown in Fig. 8, doing a much better and neater job. With the crown slitters heretofore provided it is difiicult to reach the rear or distal portion of a crown, and accordingly in a case as shown in Fig. 8 it was necessary to slit through the solder 29;

To prevent injury to the teeth or lips at one portion of the mouth when working on a crown in another portion thereof the improved slitter is curved or oifset vertically as at 30 (see Fig. 2). This curve 30 enables theinstrument to span the teeth across the jaw, either upper or lower, from a crown being worked on, and owing to this curve the instrument will also span the lips and not press or pinch them against the teeth. This is clearly shown in Figs. 6 and 7 from which figures it will be noted that the curve 30 carries the instrumentover the teeth and lips at the lower left side of the mouth while the instrument is splitting a crown at the lower right side of the mouth. Curve 30 preferably includes or is closely adjacent the pivoted portions of the members 11 and 12, and since the members have but slight relative movement at the pivot the curve carries them over or under the lower or upper teeth and lips at one side of the mouth when the instrument is being used to slit a crown on a lower or upper tooth but at the opposite side of the mouth, and movement of the handles may be had to operate the jaws without hitting or pressing on the tops of the teeth or lips on this side of the jaw- Fig. 10 shows a crown slitter constructed as the slitter previously described except that the members 31 and 32, corresponding with the members 11 and 12 of Figs. 1 and 2, do not pass one through the other but cross in side-by-side relation and are connected by a screw pivoting means 33. This form of pivoting means may be substituted for that shown in the first figures of the drawing, and it will also be understood that any other suitable form of pivotal connection between the pair of members forming handles and jaws may be employed.

From the foregoing description taken in connection with the accompanying drawing it will be apparent that with the crown slitter of the present invention crowns are slit lengthwise and may, irrespective of their position in the mouth of the patient, always be slit on the inside so that when they are resoldered and replaced in the patients mouth the solder will not be noticeable. Also, when bridges are being removed as illustrated in Fig. 8 the lateral curves 22, 23 and 24 enable the dentist to slit the crown in its thin portion rearwardly of the heavy solder 29. Also, these curves enable the dentist to get around to the rear of anterior teeth, the instrument of Figs.

1 and 2 enabling the dentist to reach the rear of all teeth from the rearmost molar to the right central tooth of the lower right, and from the 2110 left molars to the left central tooth on the upper jaw. The instrument of Fig. 9 having the curves reversed enables the dentist to reach all the other teeth. The vertical curve 30 in the instrument as above explained enables the instrument to .115 clear or span the teeth and lips at one portion of the mouth while using the instrument to split a crown in another portion and more particularly the opposite side of the mouth.

Having thus set forth the nature of my invention, what I claim is:

1. In a crown slitter, a pair of members crossed intermediate their ends to provide handle portions and jaw portions, a pivot connecting said members where they cross, one of said jaw portions comprisinga bearing jaw to rest on a crown, a knife on the other jaw portion to slit the crown, said members curved laterally in the same direction with the curve beginning at the handle side of the pivot, said members having their jaw portions beginning substantially at the pivot curved laterally in the opposite direction as said first curve, and said jaw portions having their free end portions extending at an angle to their portions adjacent the pivot and opposite to the second curve whereby said slitter may be used to slit a crown in its distal portion.

2. In a crown slitter, a pair of members crossed intermediate their ends to provide handle portions and jaw portions, a pivot connecting said members where they cross, one of said jaw portions comprising a bearing jaw to rest on a crown, a laterally curved knife on the other jaw portion to slit the crown, said members curved laterally in the same direction with the curve beginning at the handle side of the pivot, said members having their jaw portions beginning substantially at the pivot curved laterally in the opposite direction from said first curve, and said jaw portions having their free end portions extending at an angle to their portions adjacent the pivot whereby said slitter may be used to slit a crown in its distal portion.

3. In a crown slitter, a pair of members crossed intermediate their ends to provide handle portions and jaw portions, a pivot connecting said members where they cross, one of said jaw portions comprising a bearing jaw to rest on a crown, a knife on the other jaw portion to slit the crown, said members having their portions at and adjacent said pivot offset in a plane normal to the axis of said pivot whereby to span and prevent injury to the teeth and lips at one portion of the 

